First, consider a scale.

I weighed myself on the bathroom scales.

But in the last day of class,

Think of just a scale you use to measure weight.

You can actually see, right here, it will vibrate.

This is a term that's often discussed and so let's first figure out how it's calculated how do we figure this out?

I weighed myself on the bathroom scales.

Stand on the scales.

Stand on the scale.

Will the score be reliable or consistent over time.

So imagine we already have wireless scales.

So, you exercise and it picks up the exercise.

while you slide your weight

Let's examine the elevator problem one step at a time.

And a BMI is basically just taking those two numbers and using them in a little equation where you take the weight divided by the height squared.

Then, the elevator starts falling down.

You know, the kind of scale you weigh yourself on.

I hope so.

I have so much cash on hand that I actually count it by weighing it on my bathroom scale.

Since gravity hasn't changed, that must mean the scale isn't pushing up as hard.

The two forces on you are equal and opposite.

The nurse took his temperature with a thermometer.

Which means that the force of gravity pulling you down must be equal to the force of the scale pushing you up.

Here is now finally the revelation.

One, gravity pulls you down.

I bury you reverently.

Yes, I...

Newton's second law of motion net force equals mass times acceleration tells us that if the acceleration equals zero, the net force must equal zero.

Two, the scale pushes you up.

Put all your body weight against it.

Unfortunately, he's a very aggressive animal, so he's actually destroyed some of the scales.

And we see this in the inexorable march towards standardization.

How much do you weigh?

How many kilograms do you weigh?

Why is that?

Critical, nonresponsive.

I'm worried about my weight.

In the past two weeks.

And what do we do? We add some water.

Now there is a net force in the same direction as the acceleration down.

This upward push is called the normal force and yes, it is normally there.

Liquids are heavier than gases.

I woke up.

How much does this Lomu guy weigh?

He weighs 500 pounds.